Fault handling system of solid-state transformer

ABSTRACT

A fault handling system of a solid-state transformer, including a first power unit and a second power unit that are cascaded and connected is provided. The first power unit includes a first auxiliary supply, a first control module, and a first communication module. The first auxiliary supply and the first control module are both electrically connected to two ends of a first busbar capacitor. The first control module is configured to detect a voltage of the first busbar capacitor. The second power unit includes a second auxiliary supply and a second control module. The second auxiliary supply and the second control module are both electrically connected to two ends of a second busbar capacitor. The first communication module outputs fault information to the second control module when the first control module detects that the voltage of the first busbar capacitor is greater than a threshold.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Patent Application No.202111106213.9, filed on Sep. 22, 2021, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

This application relates to the field of electronic technologies, and inparticular, to a fault handling system of a solid-state transformer.

BACKGROUND

As a basic device of a power system, a conventional power transformercannot implement direct-current voltage transform. In recent years, withthe rapid development of electronic technologies, a solid-statetransformer has attracted wide attention as a new type of transformer.The solid-state transformer has an advantage of a small volume. Inaddition, the solid-state transformer can further complete tasks such aspower quality management and new energy access, and can serve as a keydevice for voltage transform and energy management in a direct-currentpower grid. Therefore, the solid-state transformer has become a currentresearch hotspot.

A medium-voltage auxiliary supply of the solid-state transformer may usea distributed structure. The auxiliary supply obtains power by using abusbar of each cascaded unit. If the auxiliary supply is damaged, abusbar capacitor of the cascaded unit damaged during medium-voltagepower-on consumes a very small quantity of charges. Consequently, thebusbar capacitor is damaged due to an increase of a busbar voltage ofthe cascaded unit.

SUMMARY

In view of this, this application provides a fault handling system of asolid-state transformer. When any cascaded power unit is faulty, anormally operating power unit can close an auxiliary supply in thenormally operating power unit and reduce a voltage of a busbar capacitorin the faulty power unit, to ensure that the voltage of the busbarcapacitor in the faulty unit is within a safe range, thereby avoidingfurther fault spreading and improving reliability of the system.

According to a first aspect, an embodiment of this application providesa fault handling system of a solid-state transformer, including a firstpower unit and a second power unit that are cascaded and connected. Thefirst power unit includes a first busbar capacitor, a first auxiliarysupply, a first control module, and a first communication module. Thefirst communication module is electrically connected to the firstcontrol module. The first auxiliary supply and the first control moduleare both electrically connected to two ends of the first busbarcapacitor. The first control module is electrically connected to thefirst auxiliary supply. The first control module is configured to detecta voltage of the first busbar capacitor. The second power unit includesa second busbar capacitor, a second auxiliary supply, and a secondcontrol module. The second control module is electrically connected tothe first communication module. The second auxiliary supply and thesecond control module are both electrically connected to two ends of thesecond busbar capacitor. The second busbar capacitor is connected inseries to the first busbar capacitor. The second control module iselectrically connected to the second auxiliary supply. The secondcontrol module is configured to detect a voltage of the second busbarcapacitor. The first communication module is configured to output faultinformation to the second control module when the first control moduledetects that the voltage of the first busbar capacitor meets a presetcondition, for example, the voltage is greater than or equal to a firstthreshold. The second control module is configured to close the secondauxiliary supply when receiving the fault information.

In this embodiment of this application, a first detection circuit in thefirst power unit detects the voltage of the first busbar capacitor.Therefore, when detecting that the voltage of the first busbar capacitoris greater than or equal to the preset threshold, the first controlmodule in the first power unit may output the fault information to thesecond control module in the second power unit by using the firstcommunication module. Based on this design, the second control modulemay close the auxiliary supply in the second power unit based on thereceived fault information. In this way, not only the voltage of thebusbar capacitor in the faulty power unit can be controlled within thesafe voltage range, but also the fault can be prevented from beingfurther spread to another normal power unit, thereby improvingreliability of the system of the solid-state transformer.

In a possible design, the first control module is configured to closethe first auxiliary supply after the first communication module sendsthe fault information to the second control module. Based on thisdesign, when the power unit is faulty, not only the fault informationcan be sent to another normally operating power unit, but also theauxiliary supply in the power unit can be closed, to avoid further faultspreading.

In a possible design, the first control module includes a firstdetection circuit, and the second control module includes a seconddetection circuit. The first detection circuit is electrically connectedto the two ends of the first busbar capacitor to detect the voltage ofthe first busbar capacitor. The second detection circuit is electricallyconnected to the two ends of the second busbar capacitor to detect thevoltage of the second busbar capacitor. Based on this design, whetherthe first power unit and the second power unit are faulty may bedetermined through detection performed by the first detection circuitand the second detection circuit.

In a possible design, the first control module further includes a firstcontrol circuit, and the second control module further includes a secondcontrol circuit. The first control circuit is electrically connected tothe first communication module. The second control circuit iselectrically connected to the first communication module. The firstcontrol circuit is configured to transmit the fault information to thesecond control circuit by using the first communication module when thevoltage that is of the first busbar capacitor and that is detected bythe first detection circuit is greater than or equal to a firstthreshold. The first control circuit controls a status of the firstauxiliary supply based on the voltage of the first busbar capacitor. Thesecond detection circuit transmits the detected voltage of the secondbusbar capacitor to the second control circuit. The second controlcircuit is configured to close the second auxiliary supply whenreceiving the fault information. Based on this design, when the firstpower unit is faulty, the second power unit may receive the faultinformation in time, and may close the auxiliary supply in the secondpower unit in time.

In a possible design, the first control module further includes a firstlatch circuit. The first latch circuit is electrically connected betweenthe first control circuit and the first auxiliary supply. The firstcontrol circuit is configured to output a first signal to the firstlatch circuit after the first communication module sends the faultinformation to the second control circuit. The first latch circuit isconfigured to close the first auxiliary supply based on the firstsignal. Based on the design of the first latch circuit, the firstauxiliary supply may be closed.

In a possible design, the second control module further includes asecond latch circuit. The second latch circuit is electrically connectedbetween the second control circuit and the second auxiliary supply. Thesecond control circuit is configured to output a second signal to thesecond latch circuit after receiving the fault information. The secondlatch circuit is configured to close the second auxiliary supply basedon the second signal. Based on the design of the second latch circuit,the second auxiliary supply may be closed.

According to a second aspect, an embodiment of this application furtherprovides a fault handling system of a solid-state transformer. The faulthandling system of the solid-state transformer includes a first powerunit and a second power unit that are cascaded and connected. The firstpower unit includes a first busbar capacitor and a first auxiliarysupply. The first auxiliary supply and the first control module are bothelectrically connected to two ends of the first busbar capacitor. Thefirst control module is electrically connected to the first auxiliarysupply. The first control module includes a first detection circuit. Thefirst detection circuit is electrically connected to the two ends of thefirst busbar capacitor. The first detection circuit is configured todetect a voltage of the first busbar capacitor. The second power unitincludes a second busbar capacitor and a second auxiliary supply. Thesecond auxiliary supply is electrically connected to two ends of thesecond busbar capacitor. The second busbar capacitor is connected inseries to the first busbar capacitor. The first control module isconfigured to close the first auxiliary supply when the first detectioncircuit detects that the voltage of the first busbar capacitor is lessthan or equal to a second threshold.

In this embodiment of this application, the first power unit and thesecond power unit are cascaded and connected. The first busbar capacitoris connected in series to the second busbar capacitor. A total voltageof the first busbar capacitor and the second busbar capacitor remainsunchanged. Therefore, if the first power unit is abnormal, the voltageof the second busbar capacitor decreases when the voltage of the firstbusbar capacitor increases. Based on this design, the first controlmodule may close the first auxiliary supply when the first detectioncircuit detects that the voltage of the first busbar capacitor is lessthan a preset threshold. In this embodiment of this application, eachpower unit may detect by using a detection circuit of each power unitwhether a voltage of a busbar capacitor decreases, and may close anauxiliary supply when it is detected that the voltage of the busbarcapacitor decreases to a threshold. Therefore, when any cascaded powerunit is faulty, a normally operating power unit can close an auxiliarysupply in the normally operating power unit and reduce a voltage of abusbar capacitor in the faulty power unit, to ensure that the voltage ofthe busbar capacitor in the faulty unit is within a safe range, therebyavoiding further fault spreading.

In a possible design, the second control module includes a seconddetection circuit. The second detection circuit is electricallyconnected to the two ends of the second busbar capacitor. The seconddetection circuit is configured to detect the voltage of the secondbusbar capacitor. Based on this design, in this embodiment of thisapplication, the first detection circuit may be used to determinewhether the first power unit is faulty.

In a possible design, the first control module further includes a firstcontrol circuit, and the second control module further includes a secondcontrol circuit. The first detection circuit is further configured totransmit the detected voltage of the first busbar capacitor to the firstcontrol circuit. The first control circuit is configured to control astatus of the first auxiliary supply based on the voltage of the firstbusbar capacitor. The second detection circuit is further configured totransmit the detected voltage of the second busbar capacitor to thesecond control circuit. The second control circuit is configured tocontrol a status of the second auxiliary supply based on the voltage ofthe second busbar capacitor. Based on this design, in this embodiment ofthis application, the statuses of the first auxiliary supply and thesecond auxiliary supply may be correspondingly controlled by using thefirst control circuit and the second control circuit.

In a possible design, the first control module further includes a firstlatch circuit. The first latch circuit is electrically connected betweenthe first control circuit and the first auxiliary supply. The firstcontrol circuit is configured to output a first signal to the firstlatch circuit when the first detection circuit detects that the voltageof the first busbar capacitor is less than a preset threshold. The firstlatch circuit is configured to close the first auxiliary supply based onthe first signal. Based on the design of the first latch circuit, thefirst auxiliary supply may be closed.

In a possible design, the second control module further includes asecond latch circuit. The second latch circuit is electrically connectedbetween the second control circuit and the second auxiliary supply. Thesecond control circuit is configured to output a second signal to thesecond latch circuit when the second detection circuit detects that thevoltage of the second busbar capacitor is less than or equal to a secondthreshold. The second latch circuit is configured to close the secondauxiliary supply based on the second signal. Based on the design of thesecond latch circuit, the second auxiliary supply may be closed.

In a possible design, the first power unit further includes a firstvoltage equalization module, and the second power unit further includesa second voltage equalization module. The first voltage equalizationmodule is connected in series to the second voltage equalization module.The first voltage equalization module is connected in parallel to thetwo ends of the first busbar capacitor. The second voltage equalizationmodule is connected in parallel to the two ends of the second busbarcapacitor. If the voltage of the first busbar capacitor is less than orequal to the second threshold and the first auxiliary supply and thesecond auxiliary supply are both in a closed state, the first voltageequalization module and the second voltage equalization module equalizethe voltages of the first busbar capacitor and the second busbarcapacitor. Based on this design, in this embodiment of this application,voltage equalization may be performed on all busbar capacitors by usingthe first voltage equalization module and the second voltageequalization module, to equalize the voltages of the first busbarcapacitor and the second busbar capacitor.

Embodiments of this application provide the fault handling system of thesolid-state transformer. When any cascaded power unit is faulty, anormally operating power unit can close an auxiliary supply in thenormally operating power unit and reduce a voltage of a busbar capacitorin the faulty power unit, to ensure that the voltage of the busbarcapacitor in the faulty unit is within a safe range, thereby avoidingfurther fault spreading, improving reliability of the system, andreducing a volume and the costs of the product.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a fault handling system of asolid-state transformer, according to an embodiment of this application;

FIG. 2 is a schematic diagram of a voltage equalization module,according to an embodiment of this application;

FIG. 3 is another schematic diagram of a voltage equalization module,according to an embodiment of this application;

FIG. 4 is another schematic diagram of a voltage equalization module,according to an embodiment of this application;

FIG. 5 is a schematic diagram of a latch circuit, according to anembodiment of this application; and

FIG. 6 is another schematic diagram of a fault handling system of asolid-state transformer, according to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

It should be noted that when an element is described as “connected to”another element, the element may be directly connected to the anotherelement, or a mediate element may simultaneously exist. When an elementis considered as “disposed in” another element, the element may bedirectly disposed in the another element, or a mediate element maysimultaneously exist.

Unless defined otherwise, all technical and scientific terms used inthis specification have the same meaning commonly understood by a personskilled in the art to which this application belongs. The terms used inthe description of this application in this specification are merely forthe purpose of describing specific embodiments, and are not intended tolimit this application. The term “and/or” used in this specificationincludes any and all combinations of one or more of the related listeditems.

FIG. 1 is a schematic diagram of cascading system architecture of afault handling system 100 of a solid-state transformer according to anembodiment of this application.

The fault handling system 100 of the solid-state transformer in thisembodiment of this application may include a plurality of power units(FIG. 1 is described by using an example of only three power units 10 a,10 b, and 10 c, and a quantity of power units may be more than three orless than three). The power units 10 a, 10 b, and 10 c may be allconfigured to convert an alternating-current voltage (for example, analternating-current medium voltage) into a direct-current low voltage oran alternating-current low voltage. In some scenarios, the mediumvoltage may be 6 kV-12 kV, and the low voltage may be 100 V-800 V. Theplurality of power units are cascaded to form the fault handling system100 of the solid-state transformer. In an embodiment, the fault handlingsystem 100 of the solid-state transformer may be formed after the powerunit 10 a, the power unit 10 b, and the power unit 10 c are cascaded. Itmay be understood that a cascading connection between the power units 10a, 10 b, and 10 c may be a series connection between input ends of thepower units 10 a, 10 b, and 10 c, and a parallel connection betweenoutput ends of the power units 10 a, 10 b, and 10 c.

It may be understood that, in this embodiment of this application, afirst alternating-current input end after the plurality of power units10 a, 10 b, and 10 c are cascaded may be connected to a first end of amedium-voltage alternating-current power grid, and a secondalternating-current input end after the plurality of power units 10 a,10 b, and 10 c are cascaded may be connected to a second end of themedium-voltage alternating-current power grid. After direct-currentoutput sides of the power units 10 a, 10 b, and 10 c are connected inparallel to form a direct-current output port, the direct-current outputport is connected to a low-voltage direct-current power grid or a load.

For example, the power unit 10 a may include an AC-DC converter 11 a, avoltage equalization module 12 a, a busbar capacitor 13 a, an auxiliarysupply 14 a, a DC-DC converter 17 a, and a control module 20 a. It maybe understood that the control module 20 a may include a latch circuit15 a, a control circuit 16 a, and a detection circuit 19 a. Theauxiliary supply 14 a may be configured to supply power to the controlmodule 20 a in the power unit 10 a. For example, the auxiliary supply 14a may supply power to the latch circuit 15 a, the control circuit 16 a,and the detection circuit 19 a. An input-end positive electrode of theAC-DC converter 11 a is electrically connected to the first end of themedium-voltage alternating-current power grid. An input-end negativeelectrode of the AC-DC converter 11 a is electrically connected to aninput-end positive electrode of the power unit 10 b. Two ends of thebusbar capacitor 13 a are respectively electrically connected to twooutput ends of the AC-DC converter 11 a. The busbar capacitor 13 a isconnected in parallel to the voltage equalization module 12 a. Theauxiliary supply 14 a is electrically connected to the two ends of thebusbar capacitor 13 a. The latch circuit 15 a is electrically connectedto the auxiliary supply 14 a and the control circuit 16 a. The controlcircuit 16 a is electrically connected to the auxiliary supply 14 a. Twoinput ends of the DC-DC converter 17 a are respectively electricallyconnected to two input ends of the AC-DC converter 11 a. Two ends of thedetection circuit 19 a are respectively electrically connected to thetwo ends of the busbar capacitor 13 a. It may be understood that, in apossible implementation, the auxiliary supply 14 a may be amedium-voltage auxiliary supply.

It may be understood that the power unit 10 b may include an AC-DCconverter 11 b, a voltage equalization module 12 b, a busbar capacitor13 b, an auxiliary supply 14 b, a DC-DC converter 17 b, and a controlmodule 20 b. The control module 20 b may include a latch circuit 15 b, acontrol circuit 16 b, and a detection circuit 19 b. The auxiliary supply14 b may be configured to supply power to the control module 20 b in thepower unit 10 b. For example, the auxiliary supply 14 b may supply powerto the latch circuit 15 b, the control circuit 16 b, and the detectioncircuit 19 b. An alternating-current input end of the AC-DC converter 11b is electrically connected to the input-end negative electrode of theAC-DC converter 11 a. An input-end negative electrode of the AC-DCconverter 11 b is electrically connected to an input-end positiveelectrode of the power unit 10 c. Two ends of the busbar capacitor 13 bare respectively electrically connected to two output ends of the AC-DCconverter 11 b. The busbar capacitor 13 b is connected in parallel tothe voltage equalization module 12 b. The auxiliary supply 14 b iselectrically connected to the two ends of the busbar capacitor 13 b. Thelatch circuit 15 b is electrically connected to the auxiliary supply 14b and the control circuit 16 b. The control circuit 16 b is electricallyconnected to the auxiliary supply 14 b. Two input ends of the DC-DCconverter 17 b are respectively electrically connected to two input endsof the AC-DC converter 11 b. Two ends of the detection circuit 19 b arerespectively electrically connected to the two ends of the busbarcapacitor 13 b. It may be understood that, in a possible implementation,the auxiliary supply 14 b may be a medium-voltage auxiliary supply.

The power unit 10 c may include an AC-DC converter 11 c, a voltageequalization module 12 c, a busbar capacitor 13 c, an auxiliary supply14 c, a DC-DC converter 17 c, and a control module 20 c. The controlmodule 20 c may include a latch circuit 15 c, a control circuit 16 c,and a detection circuit 19 c. The auxiliary supply 14 c may beconfigured to supply power to the control module 20 c in the power unit10 c. For example, the auxiliary supply 14 c may supply power to thelatch circuit 15 c, the control circuit 16 c, and the detection circuit19 c. An input-end positive electrode of the AC-DC converter 11 c iselectrically connected to the input-end negative electrode of the AC-DCconverter 11 b. An input-end negative electrode of the AC-DC converter11 c is electrically connected to the second end of the medium-voltagealternating-current power grid. Two ends of the busbar capacitor 13 care respectively electrically connected to two output ends of the AC-DCconverter 11 c. The busbar capacitor 13 c is connected in parallel tothe voltage equalization module 12 c. The auxiliary supply 14 c iselectrically connected to the two ends of the busbar capacitor 13 c. Thelatch circuit 15 c is electrically connected to the auxiliary supply 14c and the control circuit 16 c. The control circuit 16 c is electricallyconnected to the auxiliary supply 14 c. Two input ends of the DC-DCconverter 17 c are respectively electrically connected to two input endsof the AC-DC converter 11 c. It may be understood that, in a possibleimplementation, the auxiliary supply 14 c may be a medium-voltageauxiliary supply.

It may be understood that, because the power unit 10 a, the power unit10 b, and the power unit 10 c are cascaded and connected, that is, inputends of the power units 10 a, 10 b, and 10 c are connected in series,output ends of the power units 10 a, 10 b, and 10 c are connected inparallel. Based on this design, the busbar capacitor 13 a, the busbarcapacitor 13 b, and the busbar capacitor 13 c are connected in series.

In this embodiment, a direct-current output port is formed after adirect-current output side of the DC-DC converter 17 a, a direct-currentoutput side of the DC-DC converter 17 b, and a direct-current outputside of the DC-DC converter 17 c are connected in parallel or in series.The direct-current output port is connected to the low-voltagedirect-current power grid, an inverter, or a load.

If any auxiliary supply or an MCU in the fault handling system 100 ofthe solid-state transformer is faulty, a latch circuit in anothernormally operating power unit may close a corresponding auxiliarysupply. Specifically, the normally operating latch circuit may close theauxiliary supply obtaining power from a busbar. Unless the busbar ispowered on again after power failure, the auxiliary supply cannot beenabled again.

For example, the auxiliary supply 14 a in the power unit 10 a is faultyand the auxiliary supply 14 b and the auxiliary supply 14 c are bothnormal, and an output end of the auxiliary supply 14 a cannot output avoltage to the control circuit 16 a. In this case, the control circuit16 a is in a non-operating state, and a voltage of the busbar capacitor13 a increases. The busbar capacitor 13 a is connected in series to thebusbar capacitor 13 b. A total voltage of all busbar capacitorsconnected in series remains unchanged. Therefore, when a voltage of thebusbar capacitor 13 a increases, the detection circuit 19 b may detect avoltage drop of the busbar capacitor 13 b, and transmit a detectedvoltage signal to the control circuit 16 b. When a voltage of the busbarcapacitor 13 b is less than or equal to a second threshold, the controlcircuit 16 b may determine that one of cascaded power units is faulty.The control circuit 16 b outputs a control signal to the latch circuit15 b, and the latch circuit 15 b closes the auxiliary supply 14 b. Itmay be understood that the detection circuit 19 c detects a voltage dropof the busbar capacitor 13 c, and transmits a detected voltage signal tothe control circuit 16 c. When a voltage of the busbar capacitor 13 c isless than or equal to the second threshold, the control circuit 16 c maydetermine that one of the cascaded power units is faulty. The controlcircuit 16 c outputs a control signal to the latch circuit 15 c. Thelatch circuit 15 c may close the auxiliary supply 14 c. Because theauxiliary supply 14 b and the auxiliary supply 14 c are both in a closedstate, that is, the auxiliary supply 14 b and the auxiliary supply 14 cdo not operate, the voltage of the busbar capacitor 13 b and the voltageof the busbar capacitor 13 c both increase, to reduce the voltage of thebusbar capacitor 13 a and avoid an electrolyte overflow caused due tothe excessively high voltage of the busbar capacitor 13 a. In addition,the voltage equalization module 12 b and the voltage equalization module12 c may respectively perform voltage equalization on the voltage of thebusbar capacitor 13 b and the voltage of the busbar capacitor 13 c, toequalize the voltage of the busbar capacitor 13 b and the voltage of thebusbar capacitor 13 c.

The auxiliary supply 14 a in the power unit 10 a is faulty and theauxiliary supply 14 b and the auxiliary supply 14 c are both normal, andthe output end of the auxiliary supply 14 a can output a voltage to thecontrol circuit 16 a. In this case, the voltage of the busbar capacitor13 a increases. The control circuit 16 a is in an operating state, andoutputs a control signal to the latch circuit 15 a, to control the latchcircuit 15 a to close the auxiliary supply 14 a. In this case, thedetection circuit 19 b and the detection circuit 19 c respectivelydetect a voltage change of the busbar capacitor 13 b and a voltagechange of the busbar capacitor 13 c. The control circuit 16 b and thecontrol circuit 16 c respectively output control signals to the latchcircuit 15 b and the latch circuit 15 c. The latch circuit 15 b and thelatch circuit 15 c may respectively close the auxiliary supply 14 b andthe auxiliary supply 14 c. The auxiliary supply 14 a, the auxiliarysupply 14 b, and the auxiliary supply 14 c are all in the closed state.Therefore, in this case, the voltages of the busbar capacitors in allthe power units connected in series are imposed only on the voltageequalization modules. The voltage equalization modules re-allocate andequalize the voltages of the busbar capacitors in all the power unitsconnected in series, to reduce the voltage of the busbar capacitor inthe faulty power unit.

Based on this design, it can be ensured that the voltage of the busbarcapacitor in the faulty power unit is within a safe range. For example,that the busbar capacitor 13 a is connected in parallel to the voltageequalization module 12 a may be that voltage equalization isautomatically performed by using a passive component on the voltages ofthe busbar capacitors connected in series. When a voltage of one of thecapacitors connected in series increases, a current consumed on aresistor connected in parallel to the capacitor increases, to reduce thevoltage of the capacitor. In this way, the voltages of the capacitorsconnected in series are in a voltage-equalized state, to avoidout-of-control due to over-voltage caused by the positive feedback.

In this embodiment, a non-faulty power unit may detect a voltagewaveform of a busbar capacitor in the non-faulty power unit. The voltagewaveform is inconsistent with a normal voltage equalization waveform.Therefore, when the voltage waveform keeps falling, the control modulemay send a control indication to the latch circuit, to close theauxiliary supply.

FIG. 2 is a diagram of a circuit structure of a voltage equalizationmodule according to an embodiment of this application.

It may be understood that a structure of the voltage equalization module12 a is fully the same as those of the voltage equalization module 12 band the voltage equalization module 12 c. In this embodiment, thevoltage equalization module 12 a is used as an example. The voltageequalization module 12 a may include a capacitor C1, a capacitor C2, aresistor R1, and a resistor R2.

In this embodiment, a first end of the capacitor C1 is electricallyconnected to the first end of the busbar capacitor 13 a, a second end ofthe capacitor C1 is electrically connected to a first end of thecapacitor C2, and a second end of the capacitor C2 is electricallyconnected to the second end of the busbar capacitor 13 a. A first end ofthe resistor R1 is electrically connected to the first end of thecapacitor C1, a second end of the resistor R1 is electrically connectedto the second end of the capacitor C1, a first end of the resistor R2 iselectrically connected to a first end of the capacitor C2, and a secondend of the resistor R2 is electrically connected to a second end of thecapacitor C2.

FIG. 3 is a diagram of a circuit structure of a voltage equalizationmodule according to another embodiment of this application.

A difference between the voltage equalization module in this embodimentand the voltage equalization module shown in FIG. 2 is that, as shown inFIG. 3 , in this embodiment, the voltage equalization module (forexample, the voltage equalization module 12 a) may further include aZener diode D1 and a Zener diode D2.

In this embodiment, a first end of the capacitor C1 is electricallyconnected to the first end of the busbar capacitor 13 a, a second end ofthe capacitor C1 is electrically connected to a first end of thecapacitor C2, and a second end of the capacitor C2 is electricallyconnected to the second end of the busbar capacitor 13 a. A first end ofthe resistor R1 is electrically connected to the first end of thecapacitor C1, a second end of the resistor R1 is electrically connectedto a cathode of the Zener diode D1, and an anode of the Zener diode D2is electrically connected to the second end of the capacitor C1. A firstend of the resistor R2 is electrically connected to the first end of thecapacitor C2, a second end of the resistor R2 is electrically connectedto a cathode of the Zener diode D2, and an anode of the Zener diode D2is electrically connected to the second end of the capacitor C2.

FIG. 4 is a diagram of a circuit structure of a voltage equalizationmodule according to another embodiment of this application.

A difference between the voltage equalization module in this embodimentand the voltage equalization module shown in FIG. 2 is that, as shown inFIG. 4 , in this embodiment, the voltage equalization module (forexample, the voltage equalization module 12 a) may further include aZener diode D1, a Zener diode D2, a resistor R3, and a resistor R4.

In this embodiment, a first end of the capacitor C1 is electricallyconnected to the first end of the busbar capacitor 13 a, a second end ofthe capacitor C1 is electrically connected to a first end of thecapacitor C2, and a second end of the capacitor C2 is electricallyconnected to the second end of the busbar capacitor 13 a.

A first end of the resistor R1 is electrically connected to the firstend of the capacitor C1, a second end of the resistor R1 is electricallyconnected to a first end of the resistor R3, a second end of theresistor R3 is electrically connected to the second end of the capacitorC1, a cathode of the Zener diode D1 is electrically connected to a nodebetween the second end of the resistor R1 and the first end of theresistor R3, and an anode of the Zener diode D1 is electricallyconnected to the second end of the capacitor C1. A first end of theresistor R2 is electrically connected to the first end of the capacitorC2, a second end of the resistor R2 is electrically connected to a firstend of the resistor R4, a second end of the resistor R4 is electricallyconnected to the second end of the capacitor C2, a cathode of the Zenerdiode D2 is electrically connected to a node between the second end ofthe resistor R2 and the first end of the resistor R4, and an anode ofthe Zener diode D2 is electrically connected to the second end of thecapacitor C2.

FIG. 5 is a diagram of a circuit structure of a latch circuit accordingto an embodiment of this application.

It may be understood that a structure of the latch circuit 15 a is fullythe same as those of the latch circuit 15 b and the latch circuit 15 c.In this embodiment, the latch circuit 15 a is used as an example fordescription. The latch circuit 15 a may include an opto-isolator U1, aprocessing chip U2, transistors Q1-Q2, diodes D3-D4, capacitors C3-C4,an inductor L1, and resistors R5-R11.

The opto-isolator U1 may include a light-emitting unit and a switchunit. The switch unit includes an emitter and a collector. A cathode ofthe light-emitting unit is electrically connected to a node between acontrol pin 10 of the control circuit 16 a and a first end of theresistor R5, an anode of the light-emitting unit is electricallyconnected to a node between a second end of the resistor R5 and a firstend of the resistor R6, and a second end of the resistor R6 iselectrically connected to a first power supply +15 V. An emitter of theswitch unit is grounded by using the resistor R7, and a collector of theswitch unit is electrically connected to a first signal pin of theprocessing chip U2 by using the resistor R8.

A base of the transistor Q1 is electrically connected to a collector ofthe transistor Q2 and an emitter of the switch unit, an emitter of thetransistor Q1 is grounded, and a collector of the transistor Q1 iselectrically connected to the first signal pin of the processing chip U2sequentially through the resistor R9 and the resistor R10. A base of thetransistor Q2 is electrically connected to a node between the collectorof the transistor Q1 and the resistor R9, a collector of the transistorQ2 is grounded by using a capacitor C3, an emitter of the transistor Q2is electrically connected to a node between the resistor R9 and theresistor R10, a cathode of the diode D3 is electrically connected to anode between the collector of the transistor Q1 and the resistor R9, andan anode of the diode D3 is electrically connected to a second signalpin of the processing chip U2. A first end of the resistor R11 iselectrically connected to the first signal pin of the processing chipU2, the first end of the resistor R11 is further grounded by using thecapacitor C4, a second end of the resistor R11 is electrically connectedto a cathode of the diode D4, and an anode of the diode D4 is groundedby using the inductor L1.

It may be understood that the control pin IO of the control circuit 16 asends a signal to the opto-isolator U1. When a signal output by thecontrol pin IO is a low-level signal, the opto-isolator U1 is on tocontrol the transistor Q1 to be on. After the transistor Q1 is on, thebase of the transistor Q2 is pulled down to a low level state, and thesecond signal pin of the processing chip U2 is also pulled down to thelow level state. In this case, the processing chip U2 does not send acontrol signal, and the auxiliary supply 14 a has no output. Inaddition, the transistor Q1 is on, and the transistor Q1 and thetransistor Q2 may form an interlock circuit. When a busbar voltageexists, the transistor Q1 and the transistor Q2 are constantly in an onstate, and the processing chip U2 cannot reach a power-on voltage of theprocessing chip U2. Therefore, only when the busbar voltage disappearsand fully discharges, the transistor Q1 and the transistor Q2 are nolonger on, and the processing chip U2 can reach the power-on voltage ofthe processing chip U2 and start to operate normally.

In this embodiment, the control module may detect a voltage waveform ofthe busbar capacitor by using the detection circuit. For example, thecontrol circuit 16 a may detect the voltage waveform of the busbarcapacitor 13 a by using the detection circuit 19 a, determine whetherthe voltage waveform is normal, and send a corresponding control signalto the latch circuit 15 a. It may be understood that, in some possibleembodiments, the control module may be formed by a micro control unit(Micro Control Unit, MCU) and a peripheral circuit of the micro controlunit, or may be formed by a peripheral circuit of another dataprocessing control chip such as digital signal processing (digitalsignal processing, DSP) or an advanced RISC machine (Advanced RISCMachines, ARM).

FIG. 6 is a schematic diagram of another embodiment of a fault handlingsystem 100 of a solid-state transformer according to this application.

A difference between the fault handling system 100 of the solid-statetransformer in this embodiment and the fault handling system 100 of thesolid-state transformer shown in FIG. 1 is that, as shown in FIG. 6 ,each power unit in this embodiment may further include a communicationmodule, and the communication module establishes a communicationconnection to the control module.

For example, the power unit 10 a may further include a communicationmodule 18 a, the power unit 10 b may further include a communicationmodule 18 b, and the power unit 10 c may further include a communicationmodule 18 c. The communication module 18 a is connected to the controlcircuit 16 a and the communication module 18 b in a communicationmanner, the communication module 18 b is connected to the controlcircuit 16 b and the communication module 18 c in a communicationmanner, and the communication module 18 c is connected to the controlcircuit 16 c in a communication manner. For example, an operationparameter of the power unit 10 a may be transmitted to the controlcircuit in the power unit 10 b by using the communication module 18 a.An operation parameter of the power unit 10 b may be transmitted to thecontrol circuit in the power unit 10 a by using the communication module18 a. It may be understood that an auxiliary supply in each power unitmay be configured to supply power to a corresponding communicationmodule. For example, the auxiliary supply 14 a may be configured tosupply power to the communication module 18 a, the auxiliary supply 14 bmay be configured to supply power to the communication module 18 b, andthe auxiliary supply 14 c may be configured to supply power to thecommunication module 18 c.

Based on this design, signals are transmitted between the power unit 10a, the power unit 10 b, and the power unit 10 c by using thecommunication module 18 a, the communication module 18 b, and thecommunication module 18 c. When the power units in the fault handlingsystem 100 of the solid-state transformer operate normally, all thepower units may communicate with each other to transmit informationindicating that a busbar voltage is normal.

When a power unit is faulty, another normally operating power unit mayreceive fault information. The faulty power unit closes an auxiliarysupply in the faulty power unit, and transmits the fault information toan adjacent power unit, to close auxiliary supplies of all normallyoperating power units.

For example, when the power unit 10 a, the power unit 10 b, and thepower unit 10 c operate normally, communication is performed between thepower unit 10 a, the power unit 10 b, and the power unit 10 c, tomutually transmit information indicating that the voltage of the busbarcapacitor is normal. When one of the power unit 10 a, the power unit 10b, and the power unit 10 c is faulty, for example, when the power unit10 a is faulty, that is, the power unit 10 a detects by using thedetection circuit 19 a that the voltage of the busbar capacitor 13 a isgreater than or equal to a first threshold, the communication module 18a in the power unit 10 a may send the fault information to the controlmodule 20 b in the power unit 10 b. For example, the communicationmodule 18 a may send the fault information to the control circuit 16 b,and then the control circuit 16 a in the power unit 10 a outputs acontrol signal to the latch circuit 15 a, so that the latch circuit 15 acan close the auxiliary supply 14 a. When the control circuit 16 b inthe power unit 10 b receives the fault information, the control circuit16 b may further output a control signal to the latch circuit 15 b afterthe fault information of the power unit 10 a is transmitted to thecontrol circuit 16 c in the power unit 10 c, and the latch circuit 15 bmay close the auxiliary supply 14 b. After receiving the faultinformation of the power unit 10 a, the control circuit 16 c in thepower unit 10 c may transmit the fault information of the power unit 10a to a next-level power unit. The control circuit 16 c further outputs acontrol signal to the latch circuit 15 c, and the latch circuit 15 c mayclose the auxiliary supply 14 c.

Embodiments of this application provide the fault handling system 100 ofthe solid-state transformer. When any cascaded power unit is faulty, anormally operating power unit can close an auxiliary supply in thenormally operating power unit and reduce a voltage of a busbar capacitorin the faulty power unit, to ensure that the voltage of the busbarcapacitor in the faulty unit is within a safe range, thereby avoidingfurther fault spreading, improving reliability of the system, andreducing a volume and the costs of the product. A person of ordinaryskill in the art should understand that the foregoing implementationsare merely intended to describe this application but are not intended tolimit this application, provided that proper modifications and changesmade to the foregoing embodiments in the essential scope of thisapplication fall within the protection scope of this application.

What is claimed is:
 1. A fault handling system of a solid-statetransformer, comprising a first power unit and a second power unit thatare cascaded and connected, wherein: the first power unit comprises afirst busbar capacitor, a first auxiliary supply, a first controlmodule, and a first communication module, wherein the firstcommunication module is electrically connected to the first controlmodule, the first auxiliary supply and the first control module are bothelectrically connected to two ends of the first busbar capacitor, thefirst control module is electrically connected to the first auxiliarysupply, and the first control module is configured to detect a voltageof the first busbar capacitor; the second power unit comprises a secondbusbar capacitor, a second auxiliary supply, and a second controlmodule, wherein the second control module is electrically connected tothe first communication module, the second auxiliary supply and thesecond control module are both electrically connected to two ends of thesecond busbar capacitor, the second busbar capacitor is connected inseries to the first busbar capacitor, the second control module iselectrically connected to the second auxiliary supply, and the secondcontrol module is configured to detect a voltage of the second busbarcapacitor; and the first communication module is configured to outputfault information to the second control module in response to the firstcontrol module detecting that the voltage of the first busbar capacitoris greater than or equal to a first threshold and the second controlmodule is configured to close the second auxiliary supply in response toreceiving the fault information.
 2. The fault handling system of asolid-state transformer according to claim 1, wherein: the first controlmodule is further configured to close the first auxiliary supply afterthe first communication module sends the fault information to the secondcontrol module.
 3. The fault handling system of a solid-statetransformer according to claim 1, wherein: the first control modulecomprises a first detection circuit, the second control module comprisesa second detection circuit, wherein the first detection circuit iselectrically connected to the two ends of the first busbar capacitor todetect the voltage of the first busbar capacitor and the seconddetection circuit is electrically connected to the two ends of thesecond busbar capacitor to detect the voltage of the second busbarcapacitor.
 4. The fault handling system of a solid-state transformeraccording to claim 2, wherein: the first control module comprises afirst detection circuit, the second control module comprises a seconddetection circuit, wherein the first detection circuit is electricallyconnected to the two ends of the first busbar capacitor to detect thevoltage of the first busbar capacitor and the second detection circuitis electrically connected to the two ends of the second busbar capacitorto detect the voltage of the second busbar capacitor.
 5. The faulthandling system of a solid-state transformer according to claim 3,wherein: the first control module further comprises a first controlcircuit, the second control module further comprises a second controlcircuit, wherein the first control circuit is electrically connected tothe first communication module and the second control circuit iselectrically connected to the first communication module; the firstcontrol circuit is configured to transmit the fault information to thesecond control circuit by using the first communication module inresponse to the voltage of the first busbar capacitor and detected bythe first detection circuit being greater than or equal to the firstthreshold and the first control circuit controls a status of the firstauxiliary supply based on the voltage of the first busbar capacitor; andthe second detection circuit transmits the detected voltage of thesecond busbar capacitor to the second control circuit and the secondcontrol circuit is configured to close the second auxiliary supply inresponse to receiving the fault information.
 6. The fault handlingsystem of a solid-state transformer according to claim 4, wherein: thefirst control module further comprises a first control circuit, thesecond control module further comprises a second control circuit,wherein the first control circuit is electrically connected to the firstcommunication module, and wherein the second control circuit iselectrically connected to the first communication module; the firstcontrol circuit is further configured to transmit the fault informationto the second control circuit by using the first communication module inresponse to the voltage of the first busbar capacitor and detected bythe first detection circuit being greater than or equal to the firstthreshold and the first control circuit controls a status of the firstauxiliary supply based on the voltage of the first busbar capacitor; andthe second detection circuit transmits the detected voltage of thesecond busbar capacitor to the second control circuit and the secondcontrol circuit is further configured to close the second auxiliarysupply in response to receiving the fault information.
 7. The faulthandling system of a solid-state transformer according to claim 1,wherein: the first control module further comprises a first latchcircuit, wherein the first latch circuit is electrically connectedbetween the first control circuit and the first auxiliary supply, thefirst control circuit is further configured to output a first signal tothe first latch circuit after the first communication module sends thefault information to the second control circuit, and the first latchcircuit is configured to close the first auxiliary supply based on thefirst signal.
 8. The fault handling system of a solid-state transformeraccording to claim 1, wherein: the second control module furthercomprises a second latch circuit, wherein the second latch circuit iselectrically connected between the second control circuit and the secondauxiliary supply, the second control circuit is further configured tooutput a second signal to the second latch circuit after receiving thefault information, and the second latch circuit is configured to closethe second auxiliary supply based on the second signal.
 9. A faulthandling system of a solid-state transformer, comprising a first powerunit and a second power unit that are cascaded and connected, wherein:the first power unit comprises a first busbar capacitor and a firstauxiliary supply, wherein the first auxiliary supply and a first controlmodule are both electrically connected to two ends of the first busbarcapacitor, the first control module is electrically connected to thefirst auxiliary supply, the first control module comprises a firstdetection circuit, the first detection circuit is electrically connectedto the two ends of the first busbar capacitor, and the first detectioncircuit is configured to detect a voltage of the first busbar capacitor;the second power unit comprises a second busbar capacitor and a secondauxiliary supply, wherein the second auxiliary supply is electricallyconnected to two ends of the second busbar capacitor and the secondbusbar capacitor is connected in series to the first busbar capacitor;and the first control module is configured to close the first auxiliarysupply in response to the first detection circuit detecting that thevoltage of the first busbar capacitor is less than or equal to a secondthreshold.
 10. The fault handling system of a solid-state transformeraccording to claim 9, wherein: the second control module comprises asecond detection circuit, wherein the second detection circuit iselectrically connected to the two ends of the second busbar capacitorand the second detection circuit is configured to detect a voltage ofthe second busbar capacitor.
 11. The fault handling system of asolid-state transformer according to claim 10, wherein: the firstcontrol module further comprises a first control circuit and the secondcontrol module further comprises a second control circuit; the firstdetection circuit is further configured to transmit the detected voltageof the first busbar capacitor to the first control circuit and the firstcontrol circuit is configured to control a status of the first auxiliarysupply based on the voltage of the first busbar capacitor; and thesecond detection circuit is further configured to transmit the detectedvoltage of the second busbar capacitor to the second control circuit andthe second control circuit is configured to control a status of thesecond auxiliary supply based on the voltage of the second busbarcapacitor.
 12. The fault handling system of a solid-state transformeraccording to claim 10, wherein: the first control module furthercomprises a first latch circuit, wherein the first latch circuit iselectrically connected between the first control circuit and the firstauxiliary supply, the first control circuit is further configured tooutput a first signal to the first latch circuit in response to thefirst detection circuit detecting that the voltage of the first busbarcapacitor is less than or equal to the second threshold, and the firstlatch circuit is configured to close the first auxiliary supply based onthe first signal.
 13. The fault handling system of a solid-statetransformer according to claim 11, wherein: the first control modulefurther comprises a first latch circuit, wherein the first latch circuitis electrically connected between the first control circuit and thefirst auxiliary supply, the first control circuit is further configuredto output a first signal to the first latch circuit in response to thefirst detection circuit detecting that the voltage of the first busbarcapacitor is less than or equal to the second threshold, and the firstlatch circuit is configured to close the first auxiliary supply based onthe first signal.
 14. The fault handling system of a solid-statetransformer according to claim 10, wherein: the second control modulefurther comprises a second latch circuit, wherein the second latchcircuit is electrically connected between the second control circuit andthe second auxiliary supply, the second control circuit is furtherconfigured to output a second signal to the second latch circuit inresponse to the second detection circuit detecting that the voltage ofthe second busbar capacitor is less than or equal to the secondthreshold, and the second latch circuit is configured to close thesecond auxiliary supply based on the second signal.
 15. The faulthandling system of a solid-state transformer according to claim 11,wherein: the second control module further comprises a second latchcircuit, wherein the second latch circuit is electrically connectedbetween the second control circuit and the second auxiliary supply, thesecond control circuit is further configured to output a second signalto the second latch circuit in response to the second detection circuitdetecting that the voltage of the second busbar capacitor is less thanor equal to the second threshold, and the second latch circuit isconfigured to close the second auxiliary supply based on the secondsignal.
 16. The fault handling system of a solid-state transformeraccording to claim 12, wherein: the second control module furthercomprises a second latch circuit, wherein the second latch circuit iselectrically connected between the second control circuit and the secondauxiliary supply, the second control circuit is further configured tooutput a second signal to the second latch circuit in response to thesecond detection circuit detecting that the voltage of the second busbarcapacitor is less than or equal to the second threshold, and the secondlatch circuit is configured to close the second auxiliary supply basedon the second signal.
 17. The fault handling system of a solid-statetransformer according to claim 9, wherein: the first power unit furthercomprises a first voltage equalization module, the second power unitfurther comprises a second voltage equalization module, wherein thefirst voltage equalization module is connected in series to the secondvoltage equalization module, the first voltage equalization module isconnected in parallel to the two ends of the first busbar capacitor, andwherein the second voltage equalization module is connected in parallelto the two ends of the second busbar capacitor; and in response to thevoltage of the first busbar capacitor being less than or equal to apreset threshold and the first auxiliary supply and the second auxiliarysupply both being in a closed state, the first voltage equalizationmodule and the second voltage equalization module equalize the voltagesof the first busbar capacitor and the second busbar capacitor.